1. Field of the Invention
The present invention relates to a method of and system for treating waste anesthetic gas to render the gas non-poisonous. More particularly, it relates to a method of and system for treating waste anesthetic gas to decompose the laughing gas contained in the waste anesthetic gas into a nonpoisonous gas by the action of a catalyst.
2. Description of the Prior Art
Anesthetic gases mainly used in operating rooms contain laughing gas (nitrous oxide, N.sub.2 O) and halothane (1,1,1-trifluoro-2-bromo-2-chloroethane). The concentration of laughing gas in anesthetic gas is so high that it reaches 50 to 75% by volume, whereas the concentration of halothane is less than 1% by volume. The rest of the gas is oxygen. The anesthetic gas after being inhaled by a patient is discharged from the anesthetic circuit as waste anesthetic gas. The composition of the thus discharged waste anesthetic gas is approximately equal to that of the fresh inhaled anesthetic gas and thus it contains a high laughing gas content as mentioned above. The detailed composition of the waste anesthetic gas to be treated by the method and system of the present invention will be described hereinafter.
It has been revealed that the health of doctors and nurses working in operating rooms is impaired by inhaling the anesthetic gas which leaks into the operating room for a long period of time. For this reason, the National Institute for Occupational Safety and Health (NIOSH) of the United States of America has advised that the anesthetic gas concentration leaking into the operating room should be less than 25 ppm for laughing gas and less than 0.5 ppm for halothane. Unde these circumstances, the development of an effective countermeasure against contamination or pollution with the anesthetic gas in the operating room has attracted attention in recent years, and some hospitals are equipped with apparatus for discharging the waste anesthetic gases. Such apparatuses, are disclosed in Japanese Utility Model Publication No. 10159/1974 and Japanese Utility Model Laid-Open No. 52895/1977. In these discharge apparatuses, the waste anesthetic gas exhaled by a patient is sucked by a pump and immediately discharged out of the room without any treatment. Such a discharge or ventilation apparatus is in fact effective in reducing the concentration of anesthetic gas in the operating room. Moreover, it might cause a secondary pollution problem by spreading the polluting anesthetic gas into the neighborhood of the hospital. It is, therefore, necessary to remove the anesthetic component from the discharged anesthetic gas as far as possible or to convert the anesthetic component into nonpoisonous substances instead of discharging the waste anesthetic gas without treatment, when such waste anesthetic gas is discharged by using a discharge apparatus. Since halothane, one of the anesthetic gases, is readily adsorbed, by activated carbon, it may be relatively easily removed by providing the waste anesthetic discharge apparatus with an adsorption column filled with activated carbon or the like. An example of such apparatus is described in Japanese Utility Model Laid-Open No. 794/1974. However, no practically useful method of removing the laughing gas component is known.